Coral, meet the coral: How selective breeding can help the world’s reefs survive warming oceans: La Tribune India

Lismore (Australia), August 21

A single generation of selective breeding can make corals better able to withstand extreme temperatures, our new research shows.

The discovery could offer a lifeline for reefs threatened by the world’s warming oceans.

Our research, published in Science Advances, shows that corals in some of the warmest seas in the world can transfer beneficial genes associated with heat tolerance to their offspring, even when crossed with corals that have not. never experienced such temperatures.

All over the world, corals vary widely, both in terms of the temperatures they experience and their ability to withstand high temperatures without being stressed or dying. In the Persian Gulf, corals have genetically adapted to extreme water temperatures, tolerating summer conditions above 34 ° C for weeks and resisting daily averages of up to 36 ° C.

These water temperatures are 2-4 ° C warmer than any other region where corals grow, and are comparable to turn-of-the-century projections for reefs outside the Persian Gulf.

This made us wonder if beneficial gene variants could be transferred to naive coral populations at these extreme temperatures. To find out, we collected fragments of Platygyra daedalea corals from the Persian Gulf, and crossed them with corals of the same species from the Indian Ocean, where summer temperatures are much cooler.

We then heat-stressed the resulting offspring (over 12,000 individual coral larvae) to see if they could withstand temperatures of 33 ° C and 36 ° C – the summer maximums of their parents’ respective locations.

Immediate gains

We saw an immediate transfer of heat tolerance when mothers from the Indian Ocean were crossed with fathers from the Persian Gulf. These corals have shown an 84% increase in survival at elevated temperatures compared to purebred corals from the Indian Ocean, making them equally resistant to purebred corals from the Persian Gulf.

Genome sequencing confirmed that the gains in heat tolerance were due to the inheritance of beneficial genetic variants from Persian Gulf corals. Most Persian Gulf sires produced offspring that were better able to withstand heat stress, and these sires and their offspring had crucial variants associated with better heat tolerance.

Conversely, most Indian Ocean sires produced offspring that were less able to survive heat stress and were less likely to have genetic variants associated with heat tolerance.

Survival of the fittest

Encouragingly, genetic variants associated with heat tolerance were not exclusive to Persian Gulf corals. Two Indian Ocean sires produced offspring with surprisingly high survival under heat stress and had some of the same genetic variants associated with tolerance that are prevalent in Persian Gulf corals.

This suggests that some populations have genetic variation that natural selection can act on as the world’s oceans warm. Selective breeding might be able to speed up this process.

We are now evaluating the genetic basis for heat tolerance in the same coral species on the Great Barrier Reef and in Western Australia. We want to find out which genetic variants are associated with heat tolerance, how these variants are distributed in and between reefs, and whether they are the same ones that allow corals in the Persian Gulf to survive such extreme temperatures.

This knowledge will help us understand the potential of Australian corals to adapt to rapid warming.

Although our study shows that selective breeding can dramatically improve the resilience of corals to warming oceans, we do not yet know if there are tradeoffs between thermal tolerance and other important traits, and if there are risks. important genetics involved in such reproduction.

Our study was carried out on coral larvae without the algae which live in close harmony with the corals after their installation on the reefs. It will therefore also be important to examine whether genetic improvements in heat tolerance continue into the later stages of coral life, when they team up with these algae.

Of course, saving corals from the dangers of warming oceans will require action on several fronts – there are no quick fixes. Selective breeding may provide respite for some coral populations, but it will not be enough to protect entire ecosystems, nor will it replace the urgent reductions in greenhouse gas emissions needed to limit warming oceans. – The conversation


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Jeanetta J. Stewart

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